Screen reader issues

[eirikurn]

There are a few screen reader issues that we need to fix as soon as possible.

• iOS: Continue buttons are not marked as buttons for screen readers.
• iOS: Privacy policy checkbox is not marked as a checkbox so it's not clear that it should be checked.
• Android: Not possible to get through the first screen, where the language is selected. Seems like none of the buttons are marked properly.

These might be just the first few issues. We should verify the remaining screens to make sure everything works with screen readers.